This invention relates to an environmental recovery system. More particularly, but not by way of limitation, this invention relates to a system for recovering subterranean liquids from a site contaminated by hazardous waste.
During the course of industrial activities, such as petrochemical operations, certain hazardous materials are discharged unintentionally into the environment. As those of ordinary skill in the art will appreciate, these materials can ultimately contaminate the site above which the industry is situated. Furthermore, these materials can penetrate the ground soil and enter into the underlying water aquifers.
As a result, both state and federal regulatory agencies have promulgated hazardous waste clean-up programs. One of the approved methods is the extraction of the contaminated soil. Another approved process is the recovery of the insitu contaminated water through the use of recovery wells which is referred to as "pump and treat".
In the retrieval of underground water by using the recovery well process, one of the concerns is the preservation of a hydraulic gradient across the waste site which will contain the contaminated liquids in the immediate area of the recovery site. Another concern is the removal of source contaminates such as nonaqueous phase liquids (NAPL).
At the outset, it should be noted that many underground reservoirs will be shallow, and highly permeable. Thus, at the recovery site, by extracting the subterranean fluids, the hydraulic gradient in that area is lowered thereby precluding the contaminated water's migration to other uncontaminated area's. Therefore, underground water from uncontaminated areas is flowing into the site area rather than flowing out of the site area.
Various systems have been designed in order to extract the contaminated groundwater and non-aqueous phase liquids. One of the systems is the use of pumping units typically found in oil and gas fields when the hydrocarbon reservoir has ceased flowing and artificial means of producing the oil is required.
The artificial lift pumping unit utilized in the oil and gas industry comprises of a downhole pump located in a wellbore. The downhole pump is actuated by means of a string of sucker rods which extends to the surface. The sucker rod is attached to polished rod which is moved up and down by a surface pumping unit. A pumping unit is a mechanism which imparts reciprocating motion to a polished rod.
In normal oil well applications, the pump piston would be actuated by an electric motor connected to a "walking beam" arrangement. In the environmental area, the rate of groundwater recovery is generally much slower and more volatile than oil well flows; therefore, this method of actuation would be very inefficient. Flow rates from recovery wells can be as low as 0.001 gallons per minute, but can vary greatly depending on influencing conditions (e.g. local rainfall, or recharging from high levels on nearby rivers and streams, or the permeability and porosity of the reservoir, etc). Also, the size of the contaminated site may vary from several acres to several hundred acres. At the larger recovery sites, this may mean having 200 to 500 hundred pumping units.
If a conventional electric actuator was used under these conditions to maintain the recover well level below a certain point, then either the motor would be starting and stopping very frequently or the pump piston would be pumping dry. Neither of the above conditions are desirable.
Further, there is no teaching in the prior art of a system that checks whether in fact the system is pumping any of the contaminated fluid. As noted earlier, the significant amount of government regulation in this area makes having a system of checks and balances imperative. Also, the prior art does not teach, disclose nor suggest a system to insure that the proper hydraulic gradient is being maintained at the recovery site.
Therefore, there is a need for a system that will continuously monitor recovery wells and insure that the site is maintaining the proper pressure gradient in the aquifer in order to maintain the hydraulic containment. There is also a need for an apparatus which will activate only when fluid is in the wellbore thus eliminating the pump pumping dry. A system is also needed which will provide for the proper system of checks and balances for the appropriate government agency.